First of all, I would recommend a thorough dust mopping of the dry floor with a treated head. You want to remove all the grit you possibly can from the floor so the autoscrubber pad does not grind it into the finish. A properly treated head provides mild agitation and an almost magnetic attraction to soils without leaving oily residues. If the sand is still wet from melted snow, use a wet vac to remove it and get the floor dry.
Next, I would place a clean ... — Gary Clipperton, president of National Pro Clean Corp.